a. Field of the Invention
This invention pertains to bearing structures for supporting rotating machinery, and more particularly to superconducting bearing structures in which intense magnetic fields are generated by increasing the current density to resist radial or thrust forces.
b. Description of the Prior Art
Various superconducting bearing structures have been previously proposed for rotating machinery relying, for example, on the Meissner effect. One such structure is disclosed in U.S. Pat. No. 4,892,863. However, in these structures the superconductors carry internal currents induced by the motion of the shaft, hence small motions of the shaft induce small currents. As a result, in order to support large, heavy machinery shafts which are subject to large changes in radial or axial (thrust) forces, large bearing structures had to be supplied. This problem was amplified by the fact that the prior superconducting bearing structures include not only the superconducting members themselves but also the associated cryogenic equipment required to reduce the temperatures of these members to the required low temperatures. However, in many critical applications such as in aircraft or in spacecraft, both space and weight are primary considerations, which makes the prior art superconducting structures impractical because they will need large bearing structures to carry large dynamic loads.
U.S. Pat. No. 4,879,537 describes the use of high temperature superconductors for levitating magnets.